WASHINGTON (Reuters) - U.S. President George W. Bush, under fire over the treatment of CIA detainees, on Friday ordered that agency interrogators comply with Geneva Conventions against torture.

Five years after he exempted al Qaeda and Taliban members from the Geneva provisions, Bush signed an executive order requiring the CIA to comply with prohibitions against "cruel, inhuman or degrading treatment" as set down in the conventions' Common Article 3.

Bush, who insists the United States does not use torture, has faced pressure at home and abroad over interrogation techniques used on suspected militants held at secret CIA prisons and other locations, including the U.S. military prison at Guantanamo Bay, Cuba.

Critics have complained the CIA has mistreated prisoners during clandestine flights in and out of countries in Europe.

Bush's broad assertions of power in his war on terrorism also have come under assault from U.S. judges who rejected his indefinite imprisonment of enemy combatants and domestic spying program.

The new order comes 10 months after the Bush administration was forced to suspend its secret prison system because of a 2006 Supreme Court ruling that cast doubt on its legality.

CIA Director Michael Hayden said on Friday it provides clarity for CIA interrogators and other agency officials worried about the legal liabilities of their involvement in secret detention operations.

"The president's action ... gives us the legal clarity we have sought," said Hayden.

"The executive order resolves any ambiguity by setting specific requirements that, when met, represent full compliance with Article 3. Any CIA terrorist detention and interrogation effort will, of course, meet those requirements."

Fewer than 100 detainees, including suspected senior al Qaeda members, have been held in CIA secret prisons since the September 11 attacks on New York and Washington in 2001.

A smaller number has been subjected to what CIA officials describe as "enhanced interrogation measures." Human rights advocates and other critics say those methods have included techniques such as simulated drowning, or waterboarding, that amount to torture.

Senior administration officials declined to say what interrogation techniques would be allowed under the new order, arguing that the disclosure would enable al Qaeda and other militant groups to train members to resist the techniques.

The order prohibits acts including murder, torture, cruel or inhuman treatment, mutilation or maiming, intentional serious bodily injury, rape, sexual assault or abuse, biological experiments and the taking of hostages.

It bans "willful and outrageous acts of personal abuse done for the purpose of humiliating or degrading the individual in a manner so serious that any reasonable person -- considering the circumstances -- would deem the acts to be beyond the bounds of human decency."

Acts intended to denigrate a detainee's religion are also prohibited.

Officials said the administration will provide full briefings to congressional intelligence oversight committees.